ABSTRACT
We recently reported that epicatechin, a bioactive compound that occurs naturally in various common foods, promoted general health and survival of obese diabetic mice. It remains to be determined whether epicatechin extends health span and delays the process of aging. In the present study, epicatechin or its analogue epigallocatechin gallate (EGCG) (0.25% w/v in drinking water) was administered to 20-mo-old male C57BL mice fed a standard chow. The goal was to determine the antiaging effect. The results showed that supplementation with epicatechin for 37 wk strikingly increased the survival rate from 39 to 69%, whereas EGCG had no significant effect. Consistently, epicatechin improved physical activity, delayed degeneration of skeletal muscle (quadriceps), and shifted the profiles of the serum metabolites and skeletal muscle general mRNA expressions in aging mice toward the profiles observed in young mice. In particular, we found that dietary epicatechin significantly reversed age-altered mRNA and protein expressions of extracellular matrix and peroxisome proliferator-activated receptor pathways in skeletal muscle, and reversed the age-induced declines of the nicotinate and nicotinamide pathway both in serum and skeletal muscle. The present study provides evidence that epicatechin supplementation can exert an antiaging effect, including an increase in survival, an attenuation of the aging-related deterioration of skeletal muscles, and a protection against the aging-related decline in nicotinate and nicotinamide metabolism.-Si, H., Wang, X., Zhang, L., Parnell, L. D., Admed, B., LeRoith, T., Ansah, T.-A., Zhang, L., Li, J., Ordovás, J. M., Si, H., Liu, D., Lai, C.-Q. Dietary epicatechin improves survival and delays skeletal muscle degeneration in aged mice.
Subject(s)
Catechin/administration & dosage , Diet , Muscle, Skeletal/pathology , Aging/metabolism , Animals , Diabetes Mellitus, Experimental/metabolism , Male , Metabolomics , Mice , Mice, Inbred C57BL , Muscle, Skeletal/metabolism , Muscular Atrophy/metabolism , NAD/metabolism , Peroxisome Proliferator-Activated Receptors/metabolism , Survival RateABSTRACT
Termination of serotonergic transmission is the function of the plasma membrane 5-hydroxytryptamine (serotonin, 5-HT) transporter (SERT), which is also a high-affinity target in vivo for antidepressants, amphetamines, and cocaine. Studies show that SERT is regulated by protein kinase- and phosphataselinked pathways. In contrast, receptor-linked modulation of SERT is only minimally defined. Because noradrenergic stimulation is reported to influence 5-HT release, we explored possible presynaptic adrenoceptor-mediated regulation of SERT. In mouse forebrain synaptosomes, alpha2-adrenoceptor agonists, particularly 5-bromo-N-[4,5-dihydro-1H-imidazol-2-yl]-6-quinoxalinamine (UK14304), triggered a concentration- and time-dependent decrease in 5-HT transport. In contrast, 5-HT uptake was unaffected by pharmacological alpha1-adrenoceptor activation. Kinetically, UK14304 significantly decreased the apparent substrate affinity, Km without altering transport capacity, Vmax. At concentrations of UK14304 supporting maximal inhibition of SERT in synaptosomes, no effect on SERT in transfected cells was observed, suggesting that UK14304 acts indirectly to reduce SERT activity. The effect of UK14304 on 5-HT uptake was not shared by other Na+ and Cl--dependent transporters. UK14304-mediated inhibition of SERT function was yohimbine-sensitive, as was inhibition triggered by norepinephrine, and was abolished in the absence of added Ca2+. Moreover, UK14304 effects were attenuated by voltage-sensitive Ca2+ channel antagonists, consistent with a role for Ca2+ in UK14304 effects. In agreement with altered 5-HT transport activity in vitro, in vivo chronoamperometry studies revealed that UK14304 significantly prolonged 5-HT clearance. Our findings suggest that UK14304 modulates SERT function in vitro and in vivo via signaling pathways, possibly supported by an influx of Ca2+ through voltage-sensitive Ca2+ channels.
Subject(s)
Adrenergic alpha-2 Receptor Agonists , Adrenergic alpha-Agonists/pharmacology , Membrane Transport Proteins , Nerve Tissue Proteins , Quinoxalines/pharmacology , Serotonin/metabolism , Synaptosomes/drug effects , Animals , Biological Transport/drug effects , Brimonidine Tartrate , COS Cells , Calcium/metabolism , Carrier Proteins/drug effects , Carrier Proteins/metabolism , Male , Membrane Glycoproteins/drug effects , Membrane Glycoproteins/metabolism , Mice , Mice, Inbred C57BL , Serotonin Plasma Membrane Transport Proteins , Synaptosomes/metabolismABSTRACT
The calcium channel blockers (CCBs) have been shown to be effective in attenuating the behavioral effects of cocaine in rodents and subjective effects in cocaine-using volunteers. There have been reports indicating that, in the presence of toxic doses of cocaine, the CCBs could actually potentiate cocaine toxicity in rats. The present study was undertaken to make toxicological assessment of the potentiating effect of CCBs in mice. Nifedipine and nimodipine dose-dependently increased the lethalities produced by 80 mg/kg cocaine. In the presence of 40 mg/kg nifedipine, the LD50 of cocaine was decreased from 80.7 to 66.3 mg/kg. Nifedipine potentiated cocaine toxicities in both ICR and Swiss-Webster mice. The increased toxicity was not accompanied by alterations in blood electrolytes. The mechanism of increased cocaine toxicity by CCBs remains to be determined. However, our results corroborate previous findings in rats and suggest that the possibility of an antidote exacerbating the toxic effects of cocaine has to be taken into consideration when screening for therapeutic agents.
